In a random access memory (RAM) system, a memory address and read controls are applied to the RAM system to retrieve or read contents of the memory address.
In a content addressable memory (CAM) system, a data word is provided to the CAM system, and a search for the data word is performed across bits cells of the CAM. If the data word is found, the CAM system indicates a match and returns a list of one or more storage addresses where the word was found. The CAM system may also return the data word or other associated information. A CAM system may be viewed as a hardware embodiment of a software-based associative array.
A CAM system may include an array of CAM cells, each including a storage or bit cell and a compare circuit to compare contents of the bit cell with a reference bit. Conventional CAM compare circuits are implemented with complementary or differential reference bit lines, which increase routing complexity and space requirements. The compare circuits may include a separate pass circuit for each of the differential reference bit lines. Switching delays in the CAM cell can cause unwanted current contention between the separate pass circuits, which manifests itself as a crowbar current that wastes power and slows down CAM speed.
In the drawings, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears.